Giorgio Vasari, On the Restoration of The Circumcision by Signorelli (1550):
At Volterrra, over the altar of a Company in the Church of S. Francesco, he painted in fresco the Circumcision of Our Lord, which is considered beautiful to a marvel, although the Infant, having been injured by damp, was restored by Sodoma and made much less beautiful than before. And in truth, it would be sometimes better to leave works half spoilt, when they have been made by men of excellence, rather than to have them retouched by inferior masters.
From Issues in the Conservation of Paintings edited by David Bomford and Mark Leonard.
Image credit: Giovanni Battista Tiepolo (Italian, 1696-1779), Alexander the Great and Campaspe in the Studio of Apelles, ca. 1740. Detail. Oil on canvas. JPGM.
Readings in Conservation features historical writings on conservation practices from over the centuries.